Parallel Compressors Climate System

ABSTRACT

Disclosed are climate systems and methods for control the climate systems. A climate system includes a plurality of compressors arranged in parallel, a condenser disposed downstream of the compressors and an evaporator disposed downstream of the condenser. The compressors, the condenser, and the evaporator are fluidly connected by refrigerant lines to form a refrigerant circuit. The climate system also includes a controller that controls the operation of the compressors to draw back lubricant to the compressors without use of an oil equalization system.

RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application Ser.No. 62/378,135, filed Aug. 22, 2016, entitled “Parallel CompressorsClimate System,” which is incorporated by reference herein in itsentirety.

FIELD OF THE INVENTION

The present disclosure generally relates to climate systems and controlmethods therefor, and more particularly, to vehicle climate systems thatuse parallel compressors and control methods that can drawbackcompressor oil to the compressors without the use of an oil equalizationsystem.

BACKGROUND

It is well known that nearly all compressors require a form of lubricant(e.g., oil) to cool, seal, or lubricate internal components. Typically,only static jet compressors and oil-free machines with rotors suspendedin magnetic or air bearings are exempt from the need for some type oflubrication. In refrigeration systems that use compressors, a smallportion of the compressor lubricant becomes entrained with therefrigerant and discharged from the compressor. The lubricant entrainedin the refrigerant may cause several problems. For example, in a systemwith a single compressor, if too much lubricant is entrained in therefrigerant, the heat transfer and efficiency of the condenser andevaporator may be significantly reduced. In a system with two or morecompressors, in addition to affecting heat transfer and efficiency ofthe condenser and evaporator, the entrained lubricant may not bereturned to both compressors equally or properly, thereby providing toomuch lubricant to one compressor and too little to the other. Thisproblem is exacerbated when the compressors are arranged in parallel.

Some conventional systems address this by using an oil equalization linesystem that connects the compressor crankcases or oil sumps via an oilequalization line. This approach usually requires the compressors havingthe same size and the same capacity and mounted at the same level orheight. Other conventional systems use oil separators (either individualor common separators) to separate oil from the refrigerant and thenreturn the separated oil back to the compressors. These systems areinherently complicated, more expensive and/or difficult to maintain andcontrol.

Given the above background, there is a need in the art for climatesystems and control methods that are simple, less expansive and/or easyto control and at the same time can realize the benefits of the parallelcompressor configuration.

The information disclosed in this Background section is provided solelyto provide a general background of the embodiments described herein andis not an acknowledgement or suggestion that this information forms partof the prior art already known to a person skilled in the art.

SUMMARY

Various aspects of the present disclosure provide climate systems andcontrol methods that are simple to make and operate, are less expensive,and easier to control, while at the same time realizing the benefits ofa parallel compressor configuration.

In one embodiment, a climate system for cooling a compartment of avehicle is provided. The climate system includes a plurality ofcompressors, a condenser, an evaporator, refrigerant lines and acontroller. The plurality of compressors is arranged in parallel forcompressing refrigerant into a compressed refrigerant. The condenser isdisposed downstream of the plurality of compressors for condensing thecompressed refrigerant. The evaporator is disposed downstream of thecondenser for evaporating the condensed refrigerant. The evaporator isthermally coupled to the compartment of the vehicle to cool thecompartment. The refrigerant lines fluidly connect the plurality ofcompressors, the condenser, and the evaporator to form a refrigerantcircuit for circulating the refrigerant. The controller is electricallycoupled to the first and second compressors and configured toautomatically and independently control operation of the first andsecond compressors to draw back compressor oil to the first and secondcompressors.

The plurality of the compressors includes a first compressor and asecond compressor. In one embodiment, at least one of the firstcompressor and the second compressor is a twin rotary vane compressor.In another embodiment, one of the first compressor and the secondcompressor is a single rotary vane compressor. The first compressorincludes a first refrigerant inlet, a first refrigerant outlet, and afirst oil sump. The second compressor includes a second refrigerantinlet, a second refrigerant outlet, and a second oil sump. The firstrefrigerant inlet of the first compressor is fluidly connected to thesecond refrigerant inlet of the second compressor. The first refrigerantoutlet of the first compressor is fluidly connected to the secondrefrigerant outlet of the second compressor. The first oil sump isindependent of the second oil sump. In one embodiment, the first oilsump of the first compressor is independent of the second oil sump ofthe second compressor in that the first oil sump of the first compressoris not fluidly connected to the second oil sump of the secondcompressor. In another embodiment, the first oil stump of the firstcompressor is independent of the second oil sump of the secondcompressor in that the first oil sump and the second oil sump are notconnected by an oil equalizing system.

In some embodiments, the controller automatically controls operations ofthe plurality of the compressors to draw back compressor oil to thecompressors. In an embodiment, the controller operates the firstcompressor at a first low speed range for a first low-speed time periodbefore turning off the first compressor to allow compressor oil drawnback to the first oil sump. Operating the first compressor at the firstlow speed range for the first low-speed time period is performed everytime when the first compressor is turned off, every other time when thefirst compressor is to be turned off, or after the first compressor hasbeen operated at a first high speed range for a first high-speed timeperiod. In an embodiment, the controller operates the second compressorat a second low speed range for a second low-speed time period beforeturning off the second compressor to allow the compressor oil drawn backto the second oil sump. Operating the second compressor at the secondlow speed range for the second low-speed time period is performed everytime when the second compressor is to be turned off, every other timewhen the second compressor is to be turned off, or after the secondcompressor is operated at a second high speed range for a secondhigh-speed time period.

In one embodiment, the climate system further includes a sensor formeasuring an atmosphere temperature and a thermostat for receiving adesired temperature and detecting an interior temperature in thecompartment. The controller is electrically coupled to the sensor andthe thermostat and controls operations of the first and secondcompressors in accordance with the atmospheric temperature, the interiortemperature and the desired temperature.

In one embodiment, the climate system further includes a first airblower and/or a second air blower. The first air blower is positionedproximate the condenser, and configured to do one or more of thefollowing: blowing air over the condenser to cool the condenser, andvent interior air of the compartment to reduce the thermal load of thecompartment. The second air blower is configured to suck in ambient orfresh air into the compartment of the vehicle, if the interiortemperature exceeds both the desired temperature and the atmospheretemperature. The first and second air blowers can be operatedsimultaneously, alternately or independently. In some embodiments, theclimate system is integrated with an existing air conditioning system ofthe vehicle in that the first air blower and/or the second air blowerare shared by the climate system and the existing air conditioningsystem.

Another embodiment provides a first method for controlling a climatesystem. The first method includes: (a) receiving a desired temperaturefor the compartment and an atmosphere temperature outside of thevehicle; (b) monitoring an interior temperature in the compartment ofthe vehicle; (c) determining whether the interior temperature is higherthan the desired temperature; (d) determining whether the interiortemperature is higher than the atmosphere temperature; (e) turning onthe first air blower to vent interior air in the compartment, if theinterior temperature exceeds both the desired temperature and theatmosphere temperature; (f) determining whether the thermal load of thecompartment exceeds a first thermal threshold, if the interiortemperature is higher than the desired temperature but lower than orequal to the atmosphere temperature; (g) turning on the first compressoror the second compressor if the thermal load of the compartment is lessthan or equal to a first thermal threshold; and (h) turning on both thefirst compressor and the second compressor if the thermal load of thecompartment exceeds the first thermal threshold.

In some embodiments, the first method further includes one or moreadditional or optional steps. In one embodiment, the first methodincludes: operating the first compressor at a first low speed range fora first low-speed time period before turning off the first compressor toallow compressor oil drawn back to the first oil sump; and/or operatingthe second compressor at a second low speed range for a second low-speedtime period before turning off the second compressor to allow thecompressor oil drawn back to the second oil sump. In some embodiments,operating the first compressor at the first low speed range for thefirst low-speed time period is performed every time when the firstcompressor is turned off, every other time when the first compressor isto be turned off, or after the first compressor has been operated at afirst high speed range for a first high-speed time period. Operating thesecond compressor at the second low speed range for the second low-speedtime period is performed every time when the second compressor is to beturned off, every other time when the second compressor is to be turnedoff, or after the second compressor is operated at a second high speedrange for a second high-speed time period.

In some embodiments, the first method includes: determining whether itis needed to draw back compressor oil to the first compressor based onwhether the first compressor has been running at a first high speedrange and for how long; and determining whether it is needed to drawback the compressor oil to the second compressor based on whether thesecond compressor has been running at a second high speed range and forhow long. Based on the determination, the first method, in someembodiments, operates the first compressor at a first low speed rangefor a first low-speed time period to draw back compressor oil to thefirst compressor if the first compressor has been operated at the firsthigh speed range for a first high-speed time period, and/or operates thesecond compressor at a second low speed range for a second low-speedtime period to draw back compressor to the second compressor if it isdetermined that the second compressor has been operated at the secondhigh speed range for a second high-speed time period.

In one embodiment, the first method further includes: turning on asecond air blower installed in the vehicle to suck in ambient or freshair into the compartment of the vehicle, if the interior temperatureexceeds both the desired temperature and the atmosphere temperature. Inanother embodiment, the first method further includes: opening orclosing a door in a duct of the existing air conditioning system of thevehicle before turning on the second air blower, wherein the opening orclosing of the door allows the second air blower to blow the ambient orfresh air into the compartment of the vehicle.

Yet other embodiments provide a second method for controlling a climatesystem. The second method includes: (a) receiving a desired temperaturefor the compartment and an atmosphere temperature outside of thevehicle; (b) determining whether a thermal load of the compartmentexceeds a first thermal threshold; (c) turning on the first compressoror the second compressor if the thermal load of the compartment is lessthan or equal to a first thermal threshold; (d) turning on both thefirst compressor and the second compressor if the thermal load of thecompartment exceeds the first thermal threshold; and (e) performing oneor more of the following: operating the first compressor at a first lowspeed range for a first low-speed time period before turning off thefirst compressor to allow compressor oil drawn back to the first oilsump; and operating the second compressor at a second low speed rangefor a second low-speed time period before turning off the secondcompressor to allow the compressor oil drawn back to the second oilsump.

In some embodiments, prior to operating the first and/or secondcompressor at a low speed range, the second method further includes oneor more of the following additional or optional steps: determiningwhether it is needed to draw back compressor oil to the first compressorbased on whether the first compressor has been running at a first highspeed range and for how long; and determining whether it is needed todraw back the compressor oil to the second compressor based on whetherthe second compressor has been miming at a second high speed range andfor how long. After the determination, in some embodiments, the secondmethod operates the first compressor at a first low speed range for afirst low-speed time period to draw back compressor oil to the firstcompressor if the first compressor has been operated at the first highspeed range for a first high-speed time period; and operates the secondcompressor at a second low speed range for a second low-speed timeperiod to draw back compressor to the second compressor if it isdetermined that the second compressor has been operated at the secondhigh speed range for a second high-speed time period.

The systems and methods of the present disclosure have other featuresand advantages that will be apparent from or are set forth in moredetail in the accompanying drawings, which are incorporated herein, andthe following Detailed Description.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated into and constitute apart of this specification, illustrate one or more embodiments of thepresent application and, together with the detailed description, serveto explain the principles and implementations of the application.

FIG. 1 is a block diagram illustrating a climate system in accordancewith some embodiments.

FIG. 2 is a block diagram illustrating the climate system of FIG. 1,including some additional and/or optional components.

FIG. 3 is a flowchart illustrating a first exemplary method forcontrolling a climate system in accordance with some embodiments.

FIG. 4 is a flowchart illustrating the first exemplary method of FIG. 3,including some additional and/or optional steps.

FIG. 5 is a flowchart illustrating the first exemplary method of FIG. 3,including some other additional and/or optional steps.

FIG. 6 is a flowchart illustrating a second exemplary method forcontrolling a climate system in accordance with some embodiments.

DETAILED DESCRIPTION

Reference will now be made in detail to implementations of the presentapplication as illustrated in the accompanying drawings. The samereference indicators will be used throughout the drawings and thefollowing detailed description to refer to the same or like parts. Thoseof ordinary skill in the art will realize that the following detaileddescription of the present application is illustrative only and is notintended to be in any way limiting. Other embodiments of the presentapplication will readily suggest themselves to such skilled personshaving benefit of this disclosure.

In the interest of clarity, not all of the routine features of theimplementations described herein are shown and described. It will, ofcourse, be appreciated that in the development of any such actualimplementation, numerous implementation-specific decisions must be madein order to achieve the developer's specific goals, such as compliancewith application- and business-related constraints, and that thesespecific goals will vary from one implementation to another and from onedeveloper to another. Moreover, it will be appreciated that such adevelopment effort might be complex and time-consuming, but wouldnevertheless be a routine undertaking of engineering for those ofordinary skill in the art having the benefit of this disclosure.

Many modifications and variations of this disclosure can be made withoutdeparting from its spirit and scope, as will be apparent to thoseskilled in the art. The specific embodiments described herein areoffered by way of example only, and the disclosure is to be limited onlyby the terms of the appended claims, along with the full scope ofequivalents to which such claims are entitled.

Embodiments of the present disclosure are described in the context ofclimate systems for use in vehicles and methods for controlling theclimate systems. As used herein, a vehicle can be a car, a van, a truck,a bus, a trailer, or other automobiles. A climate system of the presentdisclosure in general includes two or more compressors that areconnected fluidly in parallel but with no oil equalizing system disposedthere between. The climate system also includes a condenser, anevaporator and refrigerant lines fluidly connecting the compressors,condenser and evaporators to form a refrigerant circuit. A controller isincluded in the climate system and a novel method is used to control thecompressors to draw back compressor oil that is entrained in therefrigerant or carried away by the refrigerant during operation of theclimate system. As used herein, the term “compressor oil” refers to amaterial (e.g., oil, lubricant, sealant) that is used to cool, seal orlubricate components (e.g., gears) of a compressor. In some embodiments,the compressors are controlled independently based on thermal loads.

With no oil equalizing system, the climate system of the presentdisclosure is more compact and at the same time more flexible comparedto conventional systems. For instance, the climate system can havecompressors of different sizes and different capacities, and thecompressors do not need to be mounted at the same level, height orelevation. Accordingly, the climate system of the present disclosure canbe installed in various ways such as mounted on a rear wall of a sleepercompartment in a vehicle, and/or integrated with other components in theexisting air conditioning systems of the vehicle. In addition, bycontrolling the compressors independently based on thermal loads, thepresent disclosure improves the system's overall efficiency. Inaddition, the climate system of the present disclosure requires lessparts and thus has a higher reliability and lower cost than climatesystems with more parts.

By way of illustration, FIG. 1 depicts a climate system (100) includinga plurality of compressors such as a first compressor (102) and a secondcompressor (104), a condenser (118), an evaporator (120), refrigerantlines and a controller (124). The first compressor (102) includes afirst refrigerant inlet (106) and a first refrigerant outlet (108). Thesecond compressor (104) includes a second refrigerant inlet (112) and asecond refrigerant outlet (114). The first compressor (102) and thesecond compressor (104) are fluidly connected to each other in parallelin terms of the refrigerant. For example, in the illustrated embodiment,the first refrigerant inlet (106) of the first compressor (102) isfluidly connected to the second refrigerant inlet (112) of the secondcompressor (104) by refrigerant lines (e.g., 122-6, 122-7); and thefirst refrigerant outlet (108) of the first compressor (102) is fluidlyconnected to the second refrigerant outlet (114) of the secondcompressor (104) by refrigerant lines (e.g., 122-1, 122-2).

The first compressor (102) further includes a first oil sump (110) andthe second compressor (104) includes a second oil sump (116). The firstoil sump (110) of the first compressor (102) is independent of thesecond oil sump (116) of the second compressor (104). As used herein,the term “oil sump” refers to a reservoir that houses lubricant forcooling, sealing, or lubricating internal components such as gears of acompressor. In some cases, the oil sump is a tank, an oil pan, or simplya space at the bottom of a crankcase of a compressor. In someembodiments, independency between the first oil sump (110) and thesecond oil sump (116) is characterized in that the first oil sump (110)of the first compressor (102) is not fluidly connected to the second oilsump (116) of the second compressor (104). As used herein, the first oilsump “not fluidly connected” to the second oil sump refers to one ormore of the following configurations: (i) the first and second oil sumpsare not connected by any oil equalizing system (e.g., oil line or oilconduit) that is used in conventional systems to flow oil betweendifferent oil sumps and to keep oil in different oil sumps at the samelevel, (ii) the first and second oil sumps are not connected by a commonoil separator that is used in conventional systems to separate the oilfrom the refrigerant, and (iii) the first and second oil sumps are notconnected by a common suction header or conduit that is used inconventional systems to return the oil after being separated from therefrigerant to the oil sumps.

In some embodiments, both the first and second compressors are rotaryvane compressors. In one embodiment, at least one of the firstcompressor (102) and the second compressor (104) is a twin rotary vanecompressor. In another embodiment, one of the first compressor (102) andthe second compressor (104) is a single rotary vane compressor. It willbe appreciated that the first and second compressors are not limited torotary vane (either single or twin) compressors. Any other suitablecompressors including reciprocating, scroll, screw, or centrifugalcompressors can be used in the climate system of the present disclosure.In some embodiments, the first refrigerant inlet (106) of the firstcompressor (102) includes two or more refrigerant intake ports, and thefirst refrigerant outlet (108) of the first compressor (102) includestwo or more refrigerant discharge ports. Similarly, in some embodiments,the second refrigerant inlet (112) of the second compressor (104)includes two or more refrigerant intake ports, and the secondrefrigerant outlet (114) of the second compressor (104) includes two ormore refrigerant discharge ports. In some embodiments, the two or morerefrigerant intake ports are connected to one another. In someembodiments, the two or more refrigerant outlet ports are connected toone another.

The condenser (118) is disposed downstream of the plurality ofcompressors and fluidly connected to the plurality of compressors byrefrigerant lines (e.g., 122-1, 12.2-2, 122-3). The evaporator (120) isdisposed downstream of the condenser (118) and fluidly connected to thecondenser (118) by a refrigerant line (e.g., 122-4). In someembodiments, the evaporator (120) is also fluidly connected to theplurality of compressors by refrigerant lines (e.g., 122-5, 122-6,122-7), thus forming a refrigerant circuit for circulating therefrigerant.

During operation of the climate system (100), the plurality ofcompressors compresses a refrigerant into a compressed refrigerant, thecondenser (118) condenses the refrigerant that has been compressed bythe plurality of compressors, and the evaporator (120) evaporates therefrigerant that has been condensed by the condenser (118). Theevaporator (120) is thermally coupled to a compartment of the vehicle tocool the compartment. As used herein, the term “thermally coupled”refers to one or more of the following: (i) the evaporator is mountedwithin a corresponding compartment to exchange heat with thatcompartment or with the air in that compartment, and (ii) the evaporatoris coupled with a device (e.g., heat exchanger or air blower) whichintroduces conditioned air into that compartment. The compartment can bea cab compartment, a sleeper compartment, a combination of cab andsleeper compartments, or any space in a vehicle.

As shown in FIG. 1, the controller (124) is electrically coupled to thefirst and second compressors. The controller (124) is configured toautomatically and independently control operation of the first andsecond compressors to draw back compressor oil to the first and secondcompressors. In some embodiments, to draw compressor oil that isentrained in the refrigerant or carried away by the refrigerant back tothe first oil sump (110), the controller (124) operates the firstcompressor (102) at a first low speed range for a first low-speed timeperiod before turning off the first compressor (102). In one embodiment,operating the first compressor (102) at the first low speed range forthe first low-speed time period is performed every time when the firstcompressor (102) is to be turned off. In another embodiment, operatingthe first compressor (102) at the first low speed range for the firstlow-speed time period is performed every other time when the firstcompressor (102) is to be turned off. In some embodiments, whether tooperate the first compressor (102) at a low speed range to draw backcompressor oil is determined based on how long the first compressor(102) has been running at a high speed range. For example, in someembodiments, to draw compressor oil back to the first oil sump (110),the controller (124) operates the first compressor (102) at the firstlow speed range for the first low-speed time period after the firstcompressor (102) has been operated at a first high speed range for afirst high-speed time period.

Similarly, to draw compressor oil that is entrained in the refrigerantor carried away by the refrigerant back to the second oil sump (116), insome embodiments, the controller (124) operates the second compressor(104) at a second low speed range for a second low-speed time periodbefore turning off the second compressor (104). In one embodiment,operating the second compressor (104) at the second low speed range forthe second low-speed time period is performed every time when the secondcompressor (104) is to be turned off. In another embodiment, oroperating the second compressor (104) at the second low speed range forthe second low-speed time period is performed every other time when thesecond compressor (104) is to be turned off In some embodiments, whetherto operate the second compressor (104) at a low speed range to draw backcompressor oil is determined based on how long the second compressor(104) has been running at a high speed range. For example, in someembodiments, to draw compressor oil back to the second oil sump (116),the controller (124) operates the second compressor (104) at the secondlow speed range for the second low-speed time period after the secondcompressor (104) has been operated at a second high speed range for asecond high-speed time period.

In some embodiments, the first or second low speed range is between 1500and 3000 rpm (revolutions per minute), between 1500 and 4500 rpm, orbetween 1500 and 6500 rpm. In some embodiments, the first or secondlow-speed time period before turning off the first or second compressor(104) is between 5 and 20 seconds, between 20 and 100 seconds, orbetween 100 and 200 seconds. In some embodiments, the first or secondhigh speed range is between 1500 and 3000 rpm, between 1500 and 4500rpm, or between 1500 and 6500 rpm. In some embodiments, the first orsecond high-speed time period is between 5 and 20 seconds, between 20and 100 seconds, or between 100 and 200 seconds.

In some embodiments, the controller (124) is configured to automaticallyand independently control operation of the first and second compressorsbased at least partially on a thermal load of the compartment. In someembodiments, the controller (124) turns on the first or the secondcompressor when the thermal load of the compartment is equal to or lessthan a first threshold, and turns on both the first and the secondcompressors when the thermal load of the compartment exceeds the firstthreshold. In an embodiment, the first and second compressors have thesame capacity. In another embodiment, the first and second compressorshave different capacities. In some embodiments, the first threshold ofthe thermal load corresponds to the capacity of the first or the secondcompressor. In some embodiments, the first threshold of the thermal loadis between 0.4 kW (kilowatts) and 0.8 kW, between 0.4 kW and 1.0 kW, orbetween 0.4 kW and 1.6 kW.

Referring to FIG. 2, in some embodiments, the climate system (100) ofthe present disclosure further includes other additional or optionalcomponents. For instance, in some embodiments, the climate system (100)further includes a plurality of flow control valves such as a first flowcontrol valve (204) and a second flow control valve (206). The firstflow control valve (204) is disposed upstream of the first compressor(102) and configured to selectively restrict or permit flow of therefrigerant to the first compressor (102). The second flow control valve(206) is disposed upstream of the second compressor (104) and configuredto selectively restrict or permit flow of the refrigerant to the secondcompressor (104).

In some embodiments, the climate system (100) further includes one ormore air blowers. For instance, in the illustrated embodiment, theclimate system (100) further includes a first air blower (208)positioned proximate the condenser (118). The first air blower (208) isconfigured to blow air over the condenser (118) to cool the condenser(118), and/or to vent interior air of the compartment to reduce thethermal load of the compartment. In some embodiments, the climate system(100) further includes a second air blower (214) electrically coupled tothe controller (124). The second air blower (214) is configured andcontrolled by the controller (124) to vent the interior air of thecompartment to outside, and/or to suck in the ambient or fresh air intothe compartment. In some embodiments, the climate system (100) isintegrated with an existing air conditioning system of the vehicle. Insuch cases, the first air blower (208) and/or the second air blower(214) are shared by the climate system (100) and the existing airconditioning system. In an embodiment, the first and second air blowersare mounted in the same compartment (e.g., sleep compartment or cabcompartment). In another embodiment, the first and second air blowersare mounted in different compartments, for instance, the first airblower (208) in the sleeper compartment and the second air blower (214)in the cab compartment.

To automatically control the compressors, air blowers and/or othercomponents in the system, in some embodiments, the climate system (100)of the present disclosure further includes a sensor (210) for measuringan atmosphere temperature and a thermostat (212) for setting a desiredtemperature and monitoring an interior temperature in the compartment.In such embodiments, the controller (124) is electrically coupled to thesensor (210) and the thermostat (212) and automatically controloperations of other components (e.g., air blower, compressor) based onthe atmosphere temperature, the interior temperature and the settings(e.g., desired temperature). For instance, when the interior temperatureis higher than both of the atmosphere temperature and the desiredtemperature, the controller (124) turns on the first air blower (208) tovent interior air from the compartment before turning on the first orsecond compressor. In embodiments with a second air blower (214), thecontroller (124) additionally or optionally turns on the second airblower (214) to suck in the ambient or fresh air into the compartment.As such, the thermal load is reduced before turning on the compressors,and consequently the overall efficiency of the climate system isimproved. When the interior temperature is lowered to the atmospheretemperature and the desired temperature is lower than the atmospheretemperature, the controller (124) turns on the first and/or secondcompressors to cool the compartment further down to the desiredtemperature. The controller (124) operates the first and/or secondcompressors (e.g., controlling the speed of a compressor) in accordancewith the desired temperature and the atmosphere temperature.

In some embodiments, one or more compressors are driven by electricalpower source or sources (202). In an embodiment, all of the compressorsare driven by electrical power source or sources (202). In someembodiments, at least one compressor is driven by the internalcombustion engine of the vehicle. By way of illustration, FIG. 2 showsthe first compressor (102) is configured to be driven by the internalcombustion engine, and the second compressor (104) is an electricallydriven compressor. The second compressor (104) is configured to operatewhen the internal combustion engine of the vehicle is not running.

Continuously referring to FIG. 2, in some embodiments, the climatesystem (100) of the present disclosure further includes a meteringdevice (220) disposed upstream of the evaporator (120). The meteringdevice (220) is configured to control the flow of the refrigerant intothe evaporator (120). Examples of the metering device (220) include athermal expansion valve, a capillary tube, or the like. In someembodiments, the metering device (220) is electrically coupled to thecontroller (124) and its operation is automatically controlled by thecontroller (124).

In some embodiments, the climate system (100) further includes areceiver/drier (222) disposed at the refrigerant line (122-4) betweenthe condenser (118) and the evaporator (120). The receiver/drier (222)is configured to temporarily store the refrigerant, absorb moisture fromthe refrigerant, or both.

Turning now to FIGS. 3-5, there depict a first method (300) forcontrolling climate systems in accordance with some embodiments of thepresent disclosure. For illustration purpose, the first method (300) aredescribed in the context of a climate system that includes a firstcompressor and a second compressor in parallel, i.e., the refrigerantinlets of the first and second compressors are fluidly connected to eachother and refrigerant outlets of the first and second compressors arefluidly connected to each other. The climate system further includes acondenser disposed downstream of the first and second compressors andfluidly connected to the first and second compressors, and a first airblower positioned proximate the condenser and configured to blow airover the condenser. The climate system is installed in a vehicle forcooling a compartment of the vehicle.

In some embodiments, the first method (300) is governed by instructionsthat are stored in and executed by a controller such as the controller(124) illustrated in FIGS. 1 and 2. In some embodiments, the firstmethod (300) is governed by instructions that are stored in and executedby an electronic device other than the controller (124) illustrated inFIGS. 1 and 2.

In some embodiments, the first method (300) includes: receiving adesired temperature for the compartment and an atmosphere temperatureoutside of the vehicle (step 305); monitoring an interior temperature inthe compartment of the vehicle (step 310); determining whether theinterior temperature is higher than the desired temperature (step 315);determining whether the interior temperature is higher than theatmosphere temperature (step 320); turning on the first air blower tovent interior air in the compartment, if the interior temperatureexceeds both the desired temperature and the atmosphere temperature(step 325); determining whether the thermal load of the compartmentexceeds a first thermal threshold, if the interior temperature is higherthan the desired temperature hut lower than or equal to the atmospheretemperature (step 335); turning on the first compressor or the secondcompressor if the thermal load of the compartment is less than or equalto a first thermal threshold (step 340); and turning on both the firstcompressor and the second compressor if the thermal load of thecompartment exceeds the first thermal threshold (step 345).

In some embodiments, the climate system includes a second air blower, orthe climate system is coupled to an existing air conditioning system andan air blower of the existing air conditioning system serves as a secondair blower to the climate system. In such embodiments, the first method(300) includes an additional or optional step (step 330) that turns onthe second air blower to suck in ambient or fresh air into thecompartment of the vehicle, if the interior temperature exceeds both thedesired temperature and the atmosphere temperature. The first and secondair blowers may be operated simultaneously, alternately, orindependently.

In some embodiments, the first method (300) automatically turns off thefirst compressor and/or the second compressor when the interiortemperature is lowered to the desired temperature or when cooling is nolonger desired (step 360). In some embodiments, before turning off thefirst compressor and/or second compressor, the first method (300)operates the first compressor at a first low speed range for a firstlow-speed time period before turning off the first compressor to allowcompressor oil drawn back to the first oil sump and/or operates thesecond compressor at a second low speed range for a second low-speedtime period before turning off the second compressor to allow thecompressor oil drawn back to the second oil sump (step 355).

In some embodiments, operating the first compressor at the first lowspeed range for the first low-speed time period is performed every timewhen the first compressor is to be turned off or every other time whenthe first compressor is to be turned off. Similarly, in someembodiments, operating the second compressor at the second low speedrange for the second low-speed time period is performed every time whenthe second compressor is to be turned off or every other time when thesecond compressor is to be turned off.

In some embodiments, the first method (300) further includes anadditional or optional step 405, to determine whether it is needed todraw back compressor oil to one or more compressors. If it is determinedthat drawing back compressor oil is needed for a compressor, the firstmethod (300) proceeds to step 355 to slow down that compressor (e.g.,operating that compressor at a low speed range for a period of time)before turning it off at step 360. Otherwise, the first method (300)proceeds to step 360 to turn off that compressor. In some embodiments,the determination is based on how long the compressor has been runningat a high speed range. For example, in some embodiments, operating thefirst compressor at the first low speed range for the first low-speedtime period is performed after the first compressor is operated at afirst high speed range for a first high-speed time period. Operating thesecond compressor at the second low speed range for the second low-speedtime period is performed after the second compressor is operated at asecond high speed range for a second high-speed time period.

In some embodiments, the second air blower is selectively in fluidiccommunication with the ambient, a fresh air system of the vehicle or thecompartment of the vehicle through a duct such as a pipe, a conduit, achannel, a tube or the like. In some embodiments, a door is implementedto control the air flow. In such embodiments, the first method (300)includes an additional or optional step 505, which opens or closes thedoor before turning on the second air blower to allow the second airblower to blow the ambient or fresh air into the compartment of thevehicle.

Referring to FIG. 6, there depicts a second method (600) for controllingclimate systems in accordance with some embodiments of the presentdisclosure. For illustration purpose, the second method (600) aredescribed in the context of a climate system that includes a firstcompressor and a second compressor in parallel, i.e., the refrigerantinlets of the first and second compressors are fluidly connected to eachother and refrigerant outlets of the first and second compressors arefluidly connected to each other. The climate system further includes acondenser disposed downstream of the first and second compressors andfluidly connected to the first and second compressors. The climatesystem is installed in a vehicle for cooling a compartment of thevehicle.

Like the first method (300), in some embodiments, the second method(600) is governed by instructions that are stored in and executed by acontroller such as the controller (124) illustrated in FIGS. 1 and 2. Insome embodiments, the second method (600) is governed by instructionsthat are stored in and executed by an electronic device other than thecontroller (124) illustrated in FIGS. 1 and 2.

In some embodiments, the second method (600) includes: receiving adesired temperature for the compartment and an atmosphere temperatureoutside of the vehicle (step 305); determining whether a thermal load ofthe compartment exceeds a first thermal threshold (step 335); turning onthe first compressor or the second compressor if the thermal load of thecompartment is less than or equal to a first thermal threshold (step340); turning on both the first compressor and the second compressor ifthe thermal load of the compartment exceeds the first thermal threshold(step 345); and performing one or more of the following: operating thefirst compressor at a first low speed range for a first low-speed timeperiod before turning off the first compressor to allow compressor oildrawn back to the first oil sump; and operating the second compressor ata second low speed range for a second low-speed time period beforeturning off the second compressor to allow the compressor oil drawn backto the second oil sump (step 355).

In some embodiments, prior to operating the first and/or secondcompressor at a low speed range (step 355), the second method (600)further include one or more of the following additional or optionalsteps: determining whether it is needed to draw back compressor oil tothe first compressor based on whether the first compressor has beenrunning at a first high speed range and for how long; and determiningwhether it is needed to draw back the compressor oil to the secondcompressor based on whether the second compressor has been running at asecond high speed range and for how long (step 405). Based on theresults of the determination, in some embodiments, the second method(600) further includes one or more of the following: operating the firstcompressor at a first low speed range for a first low-speed time periodto draw back compressor oil to the first compressor if the firstcompressor has been operated at the first high speed range for a firsthigh-speed time period; and operating the second compressor at a secondlow speed range for a second low-speed time period to draw backcompressor to the second compressor if it is determined that the secondcompressor has been operated at the second high speed range for a secondhigh-speed time period.

The terminology used herein is for the purpose of describing particularimplementations only and is not intended to be limiting of the claims.As used in the description of the implementations and the appendedclaims, the singular forms “a”, “an” and “the” are intended to includethe plural forms as well, unless the context clearly indicatesotherwise. It will be understood that, although the terms “first,”“second,” etc. may be used herein to describe various elements, theseelements should not be limited by these terms. These terms are only usedto distinguish one element from another. For example, a first compressorcould be termed a second compressor, and, similarly, a second compressorcould be termed a first compressor, without changing the meaning of thedescription, so long as all occurrences of the “first compressor” arerenamed consistently and all occurrences of the “second compressor” arerenamed consistently.

What is claimed is:
 1. A climate system for cooling a compartment of avehicle, comprising: a plurality of compressors for compressing arefrigerant into a compressed refrigerant, the plurality of compressorsincluding a first compressor and a second compressor, wherein the firstcompressor includes a first refrigerant inlet, a first refrigerantoutlet, and a first oil sump; the second compressor includes a secondrefrigerant inlet, a second refrigerant outlet, and a second oil sump;the first refrigerant inlet of the first compressor is fluidly connectedto the second refrigerant inlet of the second compressor; the firstrefrigerant outlet of the first compressor is fluidly connected to thesecond refrigerant outlet of the second compressor; the first oil sumpis independent of the second oil sump; and a condenser disposeddownstream of the plurality of compressors for condensing the compressedrefrigerant; an evaporator disposed downstream of the condenser forevaporating the condensed refrigerant, wherein the evaporator isthermally coupled to the compartment of the vehicle to cool thecompartment; refrigerant lines fluidly connecting the plurality ofcompressors, the condenser, and the evaporator to form a refrigerantcircuit for circulating the refrigerant; and a controller electricallycoupled to the first and second compressors and configured toautomatically and independently control operation of the first andsecond compressors to draw back compressor oil to the first and secondcompressors.
 2. The climate system of claim 1, wherein the controllerperforms one or more of the following: operating the first compressor ata first low speed range for a first low-speed time period before turningoff the first compressor to allow compressor oil to be drawn back to thefirst oil sump; and operating the second compressor at a second lowspeed range for a second low-speed time period before turning off thesecond compressor to allow the compressor oil to be drawn back to thesecond oil sump.
 3. The climate system of claim 2, wherein operating thefirst compressor at the first low speed range for the first low-speedtime period is performed each time the first compressor is to be turnedoff.
 4. The climate system of claim 1, wherein the first refrigerantinlet of the first compressor includes two or more refrigerant intakeports, and the first refrigerant outlet of the first compressor includestwo or more refrigerant discharge ports; and the second refrigerantinlet of the second compressor includes two or more refrigerant intakeports, and the second refrigerant outlet of the second compressorincludes two or more refrigerant discharge ports.
 5. The climate systemof claim 1, wherein the first oil sump of the first compressor isindependent of the second oil sump of the second compressor in that thefirst oil sump of the first compressor is not fluidly connected to thesecond oil sump of the second compressor.
 6. The climate system of claim1, wherein the first oil sump of the first compressor is independent ofthe second oil sump of the second compressor in that the first oil sumpand the second oil sump are not connected by an oil equalizing system.7. The climate system of claim 1, wherein: the first compressor isconfigured to be driven by an internal combustion engine; and the secondcompressor is an electrically driven compressor and is configured tooperate when the internal combustion engine of the vehicle is notrunning.
 8. The climate system of claim 1, further comprising: a firstflow control valve disposed upstream of the first compressor andconfigured to selectively restrict or permit flow of the refrigerant tothe first compressor; and a second flow control valve disposed upstreamof the second compressor and configured to selectively restrict orpermit flow of the refrigerant to the second compressor.
 9. The climatesystem of claim 1, wherein the controller turns on the first or thesecond compressor when the thermal load of the compartment is equal toor less than a first threshold, and turns on both the first and thesecond compressors when the thermal load of the compartment exceeds thefirst threshold.
 10. The climate system of claim 1, further comprising:a first air blower positioned proximate the condenser, and configured todo one or more of the following: (i) blowing air over the condenser tocool the condenser and (ii) vent interior air of the compartment toreduce the thermal load of the compartment.
 11. The climate system ofclaim 10, wherein the climate system is integrated with an existing airconditioning system of the vehicle, wherein the first air blower isshared by the climate system and the existing air conditioning system.12. The climate system of claim 10, further comprising; a sensor formeasuring an atmosphere temperature; and a thermostat for setting adesired temperature and monitoring an interior temperature in thecompartment; wherein the controller is electrically coupled to thesensor, the thermostat and the first air blower, and configured toperform one or more of the following: when the interior temperature ishigher than both of the atmosphere temperature and the desiredtemperature, the controller turns on the first air blower to ventinterior air from the compartment; and when the interior temperature islowered to the atmosphere temperature and the desired temperature islower than the atmosphere temperature, the controller operates at leastone of the first compressor and the second compressor, and controloperations of the first and second compressors in accordance with thedesired temperature and the atmosphere temperature.
 13. The climatesystem of claim 10, further comprising: a second air blower installed inthe vehicle and configured to suck in ambient or fresh air into thecompartment, wherein the controller is electrically coupled to thesecond air blower, and configured to perform one or more of thefollowing: controlling the first air blower to vent the interior air ofthe compartment to outside; and controlling the second air blower tosuck in the ambient or fresh air into the compartment.
 14. The climatesystem of claim 13, wherein the climate system is integrated with anexisting air conditioning system of the vehicle, wherein the first airblower and the second air blower are shared by the climate system andthe existing air conditioning system.
 15. The climate system of claim 1,further comprising a metering device disposed upstream of the evaporatorand configured for controlling flow of the refrigerant into theevaporator.
 16. The climate system of claim 15, wherein the meteringdevice is a thermal expansion valve or a capillary tube.
 17. The climatesystem of claim 1, further comprising a receiver/drier disposed betweenthe condenser and the evaporator and configured for performing one ormore of the following: temporarily storing the refrigerant and absorbingmoisture from the refrigerant.
 18. A method for controlling a climatesystem, wherein the climate system is installed in a vehicle for coolinga compartment of the vehicle, and wherein the climate system includes afirst compressor and a second compressor, wherein refrigerant inlets ofthe first and second compressors are fluidly connected to each other andrefrigerant outlets of the first and second compressors are fluidlyconnected to each other, wherein the climate system further includes acondenser disposed downstream of the first and second compressors andfluidly connected to the first and second compressors, and a first airblower positioned proximate the condenser and configured to blow airover the condenser, the method comprising: receiving a desiredtemperature for the compartment and an atmosphere temperature outside ofthe vehicle; monitoring an interior temperature in the compartment ofthe vehicle; determining whether the interior temperature is higher thanthe desired temperature; determining whether the interior temperature ishigher than the atmosphere temperature; turning on the first air blowerto vent interior air in the compartment, if the interior temperatureexceeds both the desired temperature and the atmosphere temperature;determining whether the thermal load of the compartment exceeds a firstthermal threshold, if the interior temperature is higher than thedesired temperature but lower than or equal to the atmospheretemperature; turning on the first compressor or the second compressor ifthe thermal load of the compartment is less than or equal to a firstthermal threshold; and turning on both the first compressor and thesecond compressor if the thermal load of the compartment exceeds thefirst thermal threshold.
 19. The method of claim 18, further comprising:turning on a second air blower installed in the vehicle to suck inambient or fresh air into the compartment of the vehicle, if theinterior temperature exceeds both the desired temperature and theatmosphere temperature; and opening or closing a door in a duct of theexisting air conditioning system of the vehicle before turning on thesecond air blower, wherein the opening or closing of the door allows thesecond air blower to blow the ambient or fresh air into the compartmentof the vehicle.
 20. The method of claim 18, further comprising:determining whether it is needed to draw back compressor oil to thefirst compressor based on whether the first compressor has been runningat a first high speed range and for how long; and operating the firstcompressor at a first low speed range for a first low-speed time periodto draw back compressor oil to the first compressor if the firstcompressor has been operated at the first high speed range for a firsthigh-speed time period.